Computer
29
What a Drag!
Why do you have to wear tennis shoes to your physical education class? Have you ever
worn slippery-soled dress shoes? In this lab, you will observe the differences between the
slickness of the bottom of different shoes. When the shoes are dragged across a surface,
a frictional force opposes the motion. If the bottom of shoe is slick, you will need less
force to pull it across the table because there is less friction. The opposite is also true—if
the bottom of the shoe is very sticky, or bumpy, you will need a bigger force to pull it,
because it creates a larger frictional force.
OBJECTIVES
In this activity, you will
• Make observations and predictions about shoes.
• Measure the force needed to pull different shoes across a surface.
MATERIALS
computer with Logger Lite software installed
Go! Link interface
Vernier Dual-Range Force Sensor
3 shoes with different soles
3 loops of string
KEY QUESTION
Does the material on the bottom of the shoe affect the amount of force it takes to move
it across the ground? Feel the bottom of each of the shoes. Which one feels the slickest?
Which one feels the bumpiest? Based on what you feel, complete the hypothesis below.
HYPOTHESIS
The
shoe will take the most force to pull, and the
shoe will take the least.
Elementary Science with Vernier
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Computer 29
PROCEDURE
1. Get the Force Sensor ready to collect data.
a. Make sure the Force Sensor is connected to the Go! Link and that the Go! Link is
connected to the computer.
b. Set the switch on the Force Sensor to the +/-10 N setting.
2. Start Logger Lite on your computer.
3. Open the file for this activity by doing the following:
c. Click the Open button,
.
d. Open the folder called “Elementary Science.”
e. Open the file called “29 What a Drag.”
4. Get the Force Sensor ready to collect data by doing the following:
f. Hold the Force Sensor, with the hook pointing towards the ground.
g. Look at the force values shown on the screen.
h. When the values stabilize, that is, stay the same, click
to zero the sensor.
After a few seconds, the reading should be very close to zero.
5. Attach a loop of string to the shoes in a way that will allow you to drag it across the
table.
6. Measure the weight of each of the shoes by hanging them from the Force Sensor and
record their weights in the table below. Describe the type of shoe in the table also.
Data Table
Type of shoe
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Weight of shoe
Average force
N
N
N
N
N
N
Elementary Science with Vernier
What a Drag!
7. Hook the Force Sensor to the string attached to the shoe and practice using the
Force Sensor to drag the shoe across the table. When you drag the shoe, be sure to
pull so the Force Sensor remains horizontal to the table top. Practice a few runs to
make sure you can pull the shoe slowly and steadily.
8. Follow these steps to collect data:
i. Begin slowly and steadily pulling the shoe across the table.
j. Once the shoe is moving steadily, have another person in the team click
.
k. If you reach the end of the table before the computer stops taking data, repeat
the run. You want to have a relatively steady force value for the four-second run.
9. When you have successfully collected data, click the Store button,
, to save it.
10. Repeat Steps 7–9 for each of the remaining shoes. When you have finished pulling the
shoe, be sure to click the Store button,
, to save the data.
11. When you have collected data for the all the shoes, click the Statistics button,
Select the runs that you want to see, then click
.
. Record the mean (average)
force for each of the runs in the Data Table.
Elementary Science with Vernier
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Computer 29
ANALYZE YOUR DATA
1. Was your hypothesis about the shoes correct? Tell what you observed about the shoes
that made you think this hypothesis would be true.
2. Write about the shoes that you used for this activity. What are they used for? Why
do they need less or more friction?
3. Use your data to draw some conclusions about what activities might require shoes with
more or less friction than the ones you tested. For example, what kinds of shoes do
golfers or ballet dancers wear?
Good job!!
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Elementary Science with Vernier